1. Field of the Invention
The present invention relates to an image forming apparatus and image forming method, and for example, to image forming technology for forming dots by causing ink droplets to react with treatment liquid on an image forming body.
2. Description of the Related Art
At present, an inkjet recording apparatus is used favorably as a generic image forming apparatus which outputs images captured by a digital camera or duplicates images of a printed object, or the like. An inkjet recording apparatus can use paper and other various types of recording medium such as a resin sheet, a metal sheet and the like, and the most recent tendency is to be increasing demands for the output of high-quality images, regardless of the type of recording medium.
However, there are problems in relation to print quality in that the print state varies with the paper quality, namely, with the type of the recording medium, for example, whether the medium is an OHP sheet, synthetic paper, normal paper, special inkjet paper, or the like. In particular, when printing onto normal paper using a water-soluble ink which has generic versatility, there are problems in terms of reduction in the printing resolution due to bleeding or print-through during printing, in addition to which, depending on the drying properties of the ink on the recording medium after printing, a printed image which is an undried state when the recording medium is output may be disturbed. In order to eliminate problems of this kind, a transfer recording method has been proposed in which a primary image is formed on an intermediate transfer body and the primary image is then transferred and recorded onto a recording medium.
In a transfer recording method, if the intermediate transfer body has little surface roughness, then a water repellency effect is liable to occur, whereas if the intermediate transfer body has a large surface roughness, then the transfer properties become poor, and furthermore, ink enters into the recess sections and the ink becomes smudged. Consequently, technology for forming a desirable primary image on the intermediate transfer body, and technology for improving the transfer properties when the primary image is transferred to the recording medium, have been proposed.
Japanese Patent Application Publication No. 2002-370442 describes an inkjet recording method and an image forming method which prevent a water repellency effect by providing a surface roughness of a suitable range (500 to 12000 projections with a height of 1 to 10 μm per mm2) on the surface of the intermediate transfer body.
However, if the intermediate transfer body has a high flatness, then deformation of the primary image formed on the intermediate transfer body may occur. In particular, in a two-liquid method which aggregates ink by reaction between the ink and a treatment liquid, or in a method which dries the solvent forcibly by heating, the deformation of the primary image is especially marked. On the other hand, if the surface of the intermediate transfer body is rough, then the transfer properties are poor. Furthermore, if the surface roughness of the recording medium changes, then the transfer rate (transfer properties) also varies. If a recording medium having large surface roughness, such as recycled paper, is used, then the contact surface area between the intermediate transfer body and the recording medium becomes lower and the transfer rate declines. In other words, it is extremely difficult maintain good quality in the primary image at the same time as achieving good transfer properties, and furthermore it is extremely difficult to ensure good quality of the recorded image in respect of a large number of different types of recording media.
It is an object of the invention described in Japanese Patent Application Publication No. 2002-370442 to restrict bleeding and color mixing in an ink image formed on a transfer medium (intermediate transfer body), as well as preventing water repellency effects. On the other hand, although this patent reference does mention that transfer properties deteriorate if the surface of the transfer medium is rough, concrete technology for improving the transfer properties is not disclosed. Neither is there any description of the type of recording medium or temporal change in the intermediate transfer body. In other words, the invention described in Japanese Patent Application Publication No. 2002-370442 has difficulty in responding to recording media of various types, and also has difficulty in responding to temporal change in the intermediate transfer body.